Lightweight rear derailleur tuned by Sebastian Roth

Sebastian Roth: remember his name. He is German and he is used to tuning his components to make them as light as possible, while retaining full functionality.
His latest project is the Lightweight rear derailleur. The claimed weight of this component – not
available yet – is 120g. He has modified several things and reached 91.1g!

Here are his words:

To complete my tuning-collection, I just dared myself at the Carbon-Sports rear derailleur. The basis for this, was a weight of 120g, which was surely helpful to get a very lightweight
result. After I switched from the KCNC Pulley Wheels to carbon, I saved 10g with standard serie components. But the next steps were really hard. For every half gram saved, I had to work
very hard. In comparison to the aluminium rear derailleurs I tune normally, it is far harder to save weight on a carbon basis. To drop the weight a bit more, I had to work on every
single component of the derailleur to change the materials to aluminium instead of titanium. In my opinion, the result is super with only 91,1g…